Cleaner for automotive cooling system



CLEANER FOR AuToMorrVE COOLING SYSTEM Walter Alan Hall, Springfield,Pa., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del.,a corporation of Delaware No Drawing. Application October 5, 1055 SerialNo. 538,805

1 Claim. (Cl. 252-433) This invention relates to aqueous alkalinedetergent compositions and more particularly is concerned withpackage-stable detergent compositions adapted for use in cleaningautomobile radiators and to method of preparing same. r In View of therelatively small fluid capacity of the cooling or heat exchange systemof an automobile, it is important that the system operate at maximumefiiciency to prevent loss of the fluid which can cause overheating andconsequential damage to the engine. It is desirable that the system beperiodically cleaned or purged to remove loosely bound rust, corrosionproducts, grease and oils before the detrimental deposits become tightlybound and present the probability of flaking ofi and clogging of theradiator.

There is a distinct need for a liquid detergent concentrate which can beadded to the automobile cooling system in small volume to be dilutedmany times and which in the diluted condition serves asan efflcientcleaner when circulated in the system for a period as short as 30minutes and which can remain in the system for a period as long as 24hours without harmful eifects.

An important requirement of the liquid detergent is that it must besubstantially non-foaming, otherwise foamformation would causesignificant loss of coolant from the system while the cleaning operationwas being carried out during normal operation of the vehicle.

Other important requirements desired by the user are that the detergentconcentrate shall be a liquid for convenience in introducing it into theradiator and it shall be sufficiently concentrated that a dosage of 12or 16 fluid ounces of the detergent concentrate is adequate for cleaningan automotive cooling system of average capacity. The liquid detergentconcentrate should be package-stable over a wide temperature range asthe supplier or the user may store the detergent concentrate wheretemperatures ordinarily range from sub-zero to 150 F. and higher. Oftenthe precipitated components of aqueous 'detergent compositions are noteasily redissolved after freezing and thawing, particularly the sodiumsalts. No special treatment should be required to restore the aqueousconcentrate to its original useful condition after thawing.

It is a general object of this invention to provide a detergentconcentrate having the above described desirable requirements. A morespecific object is to provide an aqueous alkaline detergent concentratefor use as an additive to the aqueous coolant of an autombile coolingsystem, which concentrate on 20 to 60 fold dilution is an efiicientcleaner for rapid dispersion of rust, corrosion products, oils andgrease and is non-foaming during normal operation of the vehicle.Another important object is to provide an aqueous detergent concentratewhich after dilution to the operative range of concentration forcleaning does not require chemical neutralization in its eliminationfrom the system, residual cleaner remaining after normal draining of thesystem 2,824,069 Patented Feb. l8, 105E:

and diluted by filling the system with water being innocuous to themetal and rubber parts of the cooling system. A further important objectis to provide an aqueous detergent concentrate comprising a salt whichredisperses upon thawing of the composition without agitation of theliquid composition. Other significant and important objects will becomereadily apparent as the description of the invention proceeds.

The objects are accomplished by preparing an aqueous liquid alkalinedetergent concentrate by dissolving in water potassium silicate,potassium chromate and potassium salts of orthophosphoric acid orequivalently the salt-forming components of the aforementioned salts,and a water-soluble salt of the polymeric condensation product ofnaphthalene sulfonic acid and formaldehyde.

The following example represents the best mode contemplated forpracticing the invention and the illustrative example is not to beconstrued as being restrictive in scope except as specifically limitedin the appended claim.

Potassium silicate solution 17.75

Sodium salt of the polymeric reaction product of naphthalene sulfonicacid and formaldehyde (Tamol-N) 3.80

The potassium hydroxide was the commercially available grade, low inchloride content, the chloride content being less than thatcorresponding to 0.5% as KCl.

The phosphoric acid was the commercially available 85% (N. F.) NationalFormulary grade.

The chromic anhydride was the commercially available grade which was ofat least 99.5% purity.

The potassium silicate solution was a commercially available aqueoussilicate solution containing an amount of silicate corresponding to12.6% K 0 and 26.5% SiO by weight, the weight ratio of K O/SiO beingabout 1:2.10. The molar ratio was about 3.3 mols of Si0 per mol of K 0.

The sodium salt of the polymeric condensation prodnet of naphthalenesulfonic acid and formaldehyde was essentially a mixture ofapproximately equal parts of dinaphthylmethane disulfonic acid and thecorresponding trimer containing three naphthalenesulfonic acid groupsper molecule, with small proportions of the higher polymers containingas many as 8 naphthalene sulfonic acid groups per molecule. Proprietaryproducts which are useful in this invention in addition to TamolNinclude Tanak A, Daxad-1l, Darvan-l, and Blancol. The potassium salt ofthe polymeric condensation product of naphthalene sulfonic acid andformaldehyde can be substituted on a pound for pound basis for thesodium salt. In the aqueous composition of the above example, thepotassium salts correspond to the approximate molar proportions of:

K20 1.000 mp0, 0.480 c ro 0.174 510 0.632

The anionic components are in the approximate molar proportions of 3mols H PO 1 mol CrtO and 4 mols sio,.

The salt-forming components. of the example were added to the water inthe .order shown, initially forming a dilute solution of potassiumhydroxide and thereafter the potassium hydroxide reacted with thephosphoric acid andchromic anhydride. As a safety precaution, mixing wascarried out in a jacketed mixer with cooling water circulating throughthe jacket, the temperature of the composition preferably beingmaintained below about 100 F.

The Composition of the example is an amber colored, clear, low viscosityliquid. The pH of the composition is about 11.1.

In order to test the eifectiveness of the detergent composition in anautomobile cooling system the following test was carried out whichsimulates the conditions which rd a il e i n anaute ob e cool t m- Theliquid detergent concentrate was diluted with water to ab u of ts O inal con sntratio w i h co nds t add o l fluid un s o the c n en a o a cl n s s cmh s a pa i of a ou qu r s A ra p a e ha in a shall s vs o abouone square inch in area and about one/sixteenth of an inch deep filledwith a weighed amount of synthetic rust/ grease mixture was suspended ina bath of the diluted detergent. The bath was thermostaticallycontrolled to a temperature in the range of about 170 to 180 i. and thebath mildly agitated by blowing air through the liquid. After thedesired cleaning period, the brass plate with. the adherent residualrust/grease mixture was removed from the bath and weighedto determinethe lossof rust/grease composition. The rust/grease composition was a50/50 uniform mixture of white petroleum and ferric oxide.

In carrying out the simulated cleaning operation described above, 50 ml.of the liquid detergent composition of the example were diluted toprovide the cleaning composition. During .a 60 minute cleaning period,0.28 gram of the rust/grease mixture was removed from the suspendedbrass plate and dispersed in the cleaning composition.

In another test sample specimens of steel, cast iron, copper, brass andaluminum, representative of metals ordinarily used in an automotivecooling system, were electrically coupled as Ordinarily found in thesystem and immersed in abath of the aerated dilute cleaning compositionofthe example. The metal specimenswere examined periodically afterimmersion in the cleaning composition and there was no significantcorrosiveattack n the eta d rin 5 days mersi n- In carrying outevaluation of the cleaner under actual pe t n ondit en one Pi quan tieso t iquid detergent concentrate-wereadded to a number of automobilecooling systems in which the fluid capacity ranged from about 10 quartsto about 22 quarts and operating temperature was controlled bythermostats opening at about 140 to 170 1?. The cleaning cycle rangedfrom about minutes after the thermostat opened to about 24 hours. Duringthe cleaning period some automobiles had been driven up to about 200miles under normal operating conditions. After the cleaning cycle, thecooling system was drained, filled with water and redrained. Draining ofthe system ordinarily removes only a major portion. of the fluid fromthe system. While the residual spent cleaner after the first drainingfurther diluted by filling the system with water can remain in thesystem without hazard, it is preferred to flush the residual cleanerfrom the system, particularly when the initially drained lignid issignificantly discolored with rust. In such instances, ilushingwaswaccomplished by filling the 5 8 Wit w ltfirafter theinitial drainingand redraining, repeating the operation several times if necessary untilthe drain water was clear. Alternatively, water can be. introducedcontinuously to flush the system until the effiuent water is clear.

Where the system to be cleaned contained alcoholtype or glycol-typeanti-freeze, the system was drained of the anti-freeze and filled withwater prior to addition of the detergent concentrate.

In all of these practical tests, cleaning action was efiicient, therewas no foaming and the operation was convenient, simple and rapid.Flushing equivalent to one fill of the system with water followed bydraining and a refill with water was found to be ordinarily adequate.Neutralization of residual cleaner in the system was not required evenwhen the flushing step was omitted and the normal undrainable content ofthe system was merely diluted with water to the normal volume of thesystem. At this dilution and at greater dilution associated with simpleflushing, the aqueous coolant finally remaining in the system was mildlyalkaline and desirably in the pH range of about 7.2 to 8.5.

The liquid detergent concentrate packaged in conventional tinplatecontainers having a coating weight of 0.5 pound of tin waspackage-stable and non-corrosive toward the interior surface of thecontainer when stored fora period as long as nine months at atmospherictemperature ranging from about 65 F. to 100 F. Acceleratedtestsconducted in an oven at 120 F. for nine months also indicated excellentpackage-stability.

aqlif ge-stability or freeze-thaw resistance at temperatures below thefreezing point of the concentrate were more significant. Packages of theliquid detergent concentrate subjected to three freeze-thaw cycles withexposure for 16 hours at 0 to 4 F. followed "by thawing duringstoragefor 4 to 6 hours at about 77 F, showed that the composition wasfreeze-thaw resistant and package stable under freezing conditions.Solid matter formed during freezing thawed to liquid condition withoutagitation. In contrast, a similar composition formulated with equivalentamounts of the corresponding sodium salts substituted for the potassiumsalts of the example was poor in freeze-thaw resistance. The sodiumsalts precipitated during freezing redissolved slowly, requiringmechanical agitation and heating to effect solution of the salts.

When substantial proportions of the sodium salts are in combination withthe preferred potassium salts, the product continues to show thedeficiency in freeze-thaw resistance. It is not necessary that sodiumsalts be entirely absent from the composition, but the significantadvantages residing in the use of the potassium salts are diminished toless than a practical advantage when the potassium ion' is decreased tobelow about mol percent of the total mols of alkali metal present in thecomposition. It is preferred that the potassium represents at least molpercent of the total alkali metal. The sodium ion contribution of thewater-soluble surface active salt is insignificant, however thepotassium salt of the polymeric condensation product of naphthalenesulfonic acid and formaldehyde can be substituted for the sodium salt ofthe example.

While ammonium and amine salts of the polymeric condensation product ofnaphthalene sulfonic acid and formaldehyde are also useful substitutesfor the sodium salt specified in the example, the presence of theseammonium salts is less desirable because of potential corrosive attackon copper and copper-containing metals, such as brass. However, theuseful concentration. of surface active ammonium salts of the dilutecleaner remaining in the system for as long as 24.ho urs exhibits nosignificant corrosive attack on copper.

Although theexample shows in situ formation of the pertinent phosphateand chromate salts, equivalent proportions of potassium orthophosphateand .jpotassium chromate can be substituted for the salt-formingconstituents,

.While potassium silicate having a molar ratioof about 3.3 rn ols of SiOper mol of K 0 is preferred, other commercially available gradesofpotassium silicate in which K 1.00 sio 0.60 10 0.70 H3170; to CIO 0.15100.20

It is preferred that the mols of SiO approximately equal the total molsof H PO and CrO The content of the water soluble salt of the polymericcondensation product of naphthalene sulfonic acid and formaldehyde isnot significantly critical. A content of at least 1% based on the weightof the aqueous concentrate is required to provide a practicalimprovement in the speed of dispersing rust and grease in the aqueoussolution. The preferred amount of the surface active agent is in therange of 2% to 5% based on the total composition. No practical advantagewas seen in using an amount greater than about 7.5%, based on totalcomposition.

While the presence of the preferred amount of the surface active agentsignificantly enhanced the speed of the cleaning operation to the extentthat cleaning was efiiciently accomplished in a period as short as 30minutes, the surface active agent within the same concentration rangeused as the sole cleaning agent in the absence of the pertinent mixtureof phosphate, silicate and chromate salts, was inefficient in itsoperation and impractical as a cleaner for the intended purpose.

For a practical dosage of either 12 fluid ounces or 16 fluid ounces ofdetergent concentrate for an automobile cooling system of averagecapacity, 100 parts by weight of the liquid detergent concentratepreferably contains from about 20 to 30 parts by weight of the mixtureof phosphate, chromate and silicate salts. The concentrate can beproportionately lower in salt content when the dosage is one quartinstead of one pint, but packaging a dosage of this larger size at thelower concentration is not economical. The dosage of 12 to 16 fluidounces in an automobile cooling system ranging in capacity from to about22 quarts corresponds to dilution of the concentrate from about 20 timesto about 60 times the original volume. The concentration of the mixtureof phosphate, chromate and silicate salts preferably is in the range ofabout 0.5% to 1.5% based on the weight of the diluted cleaning solution.In cooling systems of higher capacity, it is desirable to increase thedosage to two 12 to 16 fluid ounce units in order that the concentrationon dilution is preferably within the indicated range of saltconcentration.

This invention provides a significant advance in liquid alkalinedetergent concentrates adapted for use on 20 to fold dilution as anon-foaming cleaning composition for efficient removal of rust,corrosion products, oils and greases from an automotive cooling system.The cleaner can be used while the automobile is in normal operation.Flushing to counteract the concentration of spent cleaner can beminimized, the object of flushing being primarily to eliminate dispersedrust, oils and grease rather than to dilute the residual spent cleaner.Chemical neutralization of the spent cleaner is not essential.

While there are above disclosed but a limited number of embodiments ofthe structure, process and product of the invention herein presented, itis possible to produce still other embodiments without departing fromthe inventive concept herein disclosed, and it is desired therefore thatonly such limitations be imposed on the appended claim as are statedtherein, or required by the prior art.

I claim:

An aqueous detergent concentrate adaptable as a cleaner for anautomotive cooling system on dilution to 20 to 60 times its originalvolume, comprising the following approximate composition:

Parts by weight Water 56.25 Potassium hydroxide, 13.20 Phosphoric acid,85 6.85 Chromic anhydride 2.15

Potassium silicate solution containing 12.6% K 0 and 26.5% Si0 17.75

Sodium salt of the polymeric reaction product of naphthalene sulfonicacid and formaldehyde 3.80 W656 References Cited in the file of thispatent UNITED STATES PATENTS 1,962,821 Kochs June 12, 1934 2,326,837Coleman Aug. 17, 1943 2,439,784 Cerna Apr. 13, 1948 2,503,381 EichwaldApr. 11, 1950 2,614,992 Mankowich Oct. 21, 1952 2,740,734 Dinley Apr. 3,1956

